Musnad Abu Ya'la al-Mawsili 155:236

Mujahid ibn Musa narrated to us, Abdullah ibn Bakr narrated to us, Hisham narrated to us, from Muhammad, from Abu Hurairah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Let not one of you urinate in stagnant water, then perform ghusl (full ablution) from it."